An increasing number of surgical procedures are being performed using minimally invasive techniques. Many of these techniques involve a physician operating internally on a patient's body through a relatively small opening. The small opening can be obtained percutaneously by opening a tract into a patient's body, by utilizing an existing body lumen, or by a combination of both techniques. Once a tract has been opened, a sheath is often necessary to maintain the tract open, for example to facilitate insertion, placement, and removal of catheters and other medical instruments, such as an arthroscope or a stent. A sheath is also useful for draining fluids from a body, such as urine from a kidney or bladder, and for inserting fluids, such as a contrasting agent for a radiograph, into a body.
One particular medical procedure using a sheath is a nephrostomy, in which an opening is surgically formed between a renal pelvis and the outside of the body. Generally, a small tract is made with a needle, or trocar, through a patient's body (i.e., the back), through the cortex of the kidney, and into the renal pelvis. Once formed, the small tract is expanded to a predetermined size to accommodate medical instruments and/or removal of a renal calculi (i.e., a stone). Once the tract has been expanded, a sheath can be inserted along the length of the tract extending from outside the patient's body to the internal target area. The expanding instruments can then be removed, for example, through the sheath. A guide wire, however, is often left within the sheath to facilitate repositioning of the sheath should that be necessary, and to facilitate insertion and removal of medical instruments. Once properly installed, a physician is then free to perform the intended medical procedure through the tract formed by the sheath. Upon completion of the procedure, the sheath is removed from the patient's body and any incision is closed.
Sheaths as described above are commercially available in standard or preselected sizes, the diameters and lengths typically depending on a particular application. Exemplary sheaths include the FLEXOR® ureteral access sheath available in internal diameters ranging from 9.5 French units (Fr) to 12.0 Fr, and lengths ranging from 20 cm (order no. FUS-095020) to 55 cm (order no. FUS-120055), the sheath of the N-CIRCLE® Nitinol Tipless Stone Extractor (e.g., order no. NTSE-022115-UDH), and the N-Force® Nitinol Helical Stone Extractor (e.g., order no. NFHSES-032115-3W-UDH), all manufactured by Cook Urological, Inc., of Spencer, Ind. Other sheaths are commercially available, such as the Examining Ureteral Sheath (catalog no. HUS-10S) and the Operating Ureteral Sheath (catalog no. HUS-12S), both manufactured by ACMI Corp. of Southborough, Mass.
Unfortunately, these and other commercially available sheaths are unavailable for some patients, as the standard sizes are inadequate. In particular, the commercially available nephrostomy sheaths can be too short for obese patients. Use of a sheath that is too short can result in procedural complications. For example, a sheath extending outside of the patient's body can pull away from a target location within a patient's body. Alternatively, a sheath remaining fixed to a target location can recess completely within a patient's body. Either scenario would unnecessarily complicate the related procedure and increase risk to the patient.